Exothermic mixture



Patented Nov. 4, 1941 UNITED STATES PATENT OFFICE EXOTHERMIC MIXTUREWalter M. Brunet, Wilmington, Del., assign'or to W. G. Shelton Company,St. Louis, Mo., a cornotation of Missouri No Drawing. Application June3, 1940,

7 Serial No. 338,585

' claims.- (01. 44-3) actions involved must be controlled withinwelldefined limits as to the degree of heat and as to the extent of theheating period, all as is well understood in the art.

One object of the present invention is to produce exothermic chemicalcompositions in which the degree and duration of heat may be accuratelycontrolled for the specific use intended.

Many exothermic compositions at present man- .ufactured suffer fromtheir undue sensitivity to deteriorating influences such as the effectsof atmospheric' moisture, oxygen, and carbon dioxide on the composition.Compositions which are adversely affected by these components arecharacterized by a declining amount of heat available from thecomposition, the extent of the heat loss being dependent upon suchfactors as temperature, humidity, the protection imparted by the packageand the time elapsed since manufacture. It is another object of thisinvention to produce compositions which are stable to atmosphericinfiuences without requiring reliance upon such expedients asmoisture-proof wrappings, sealed metalllc containers, and the like.

A further object of this invention is to produce exothermic compositionsfrom readily available materials which require no special care inhandling and which may be incorporated into a mixture of suitablephysical form by the use of simple manufacturing equipment and withoutspecial control measures.

Another object of the invention is to avoid the use of substances whichare toxic and might affect the comfort or health of the users, andparticularly operators who handle the pads over extended periods. Someacidic substances which have been proposed for use in exothermic pads(oxalic acid, for example) may give rise to allergic disturbances in theoperators.

Another object of the invention is to avoid the use of substances whichare unduly volatile in reactions (hydrochloric acid, for example) andare likely to be emitted from the pads, and may be particularlyobjectionable because of a tendency to attack metal parts of equipmentused with the pads.

The present invention contemplates the use of ordinary water as amoistening medium which when suitably applied to the exothermiccomposition presently to be described initiates the. evolution of heatby means of oxidation-reduction reactions.

An important component oi! the exothermic composition is a metal or amixture of metals. Such metals as iron, aluminum, copper, tin, bismuth,antimony, lead, magnesium, zinc, cadmium, manganese, or alloys of thesame and other metals function well in exothermic compositions. However,aluminum is preferred as the principal metallic component by reason ofits cheapness, convenience, and the high heat of formationof itscompounds. The purpose of this component is to supply heat by means ofitsoxidation. Experiment has shown that the duration of the heatingperiod may be controlled by means of the oxidize the metal. Thiscomponent may be any one or a mixture of more than oneof such highlyoxygenated compounds as potassium dichromate, barium peroxide, benzoylperoxide or other organic peroxides, potassium permanganate, thepersulfate of ammonium and the alkali metals, the chlorites, chloratesand perchlorates of magnesium and the alkali metals, the perborates ofthe alkali metals, and the like. However, because of solubilitycharacteristics, economy, and particularly because of the highlyoxidizing decomposition products which are formed when it is acidified,potassium chlorate is one of the most convenient oxidizing agents touse. In practice it is found that the proportion 'of this component hasa pronounced effect upon the time temperature relationship of theheating period which follows the moistening oi the composition.

Certain oxides of metals which are lower in the eiectromotive seriesthan the base metal selected for the composition, as, for example,cuprous and cupric oxides, are valuable addition agents. They acceleratethe evolution of heat, evidently by means of replacement reactions. Thepreferred oxide is cuprous oxide.

Another component of the reaction is an acidic substance stable in thedry 'state. The group of compounds known as'the organic sulfonic acidsare eminently suited to perform the function' of this component. Sincethis class of organic compounds is very large, ,and continually growinglarger, it is impossible to name all of the sulfonic acids which willfunction. However, all sulfonic acids which when placed in pure water inthe proportion of one gram of sulfonic acid to ten grams of water form amixture which is suiliciently acidic to redden a piece of blue litmuspaper are considered an integral part of the invention. The solidsulfonic acids are preferred. These sulfonic acids may in general berepresented by the formula, RSOaH, where R. is a substituted orunsubstituted, aliphatic or aromatic radical. The organic acid sulfatesare also included in this class of components; these may be representedby the formula R'OSOaH where R. is a substituted or unsubstituted,aliphatic or aromatic radical.

.As examples of this class of compounds containing the grouping -SOaH,benzene sulfonic acid and paratoluene sulfonic acid may be cited.

The organic sulflnic acids are also included in this class ofcomponents; these may be represented by the formula R"SO:H, where R." isa substituted or unsubstituted, aliphatic or aromatic radical.

The acidic substance contemplated may be defined as an organic acidcontaining sulfur as a part of the acid group, that is, a group of atomscontaining sulfur which confers acidity on the chemical structure as awhole. This includes the sulfonic acid group --SO:H, acid sulfate group-OSO3H, sulfinic acid group S0:H.

The above-mentioned acidic media possesses advantages over substancespreviously used for the same purpose in that they are solid, relativelynon-hygroscopic, non-corrosive, acidic chemical entities which need notbe evolved from auxiliary reactions in order to function in anexothermic mixture, and are unusually stable or passive in the presenceof metals such as are likely to be used in exothermic mixes.

Another component of the composition is an inert material whichfunctions as a diluent for the active components. This component maycomprise one or more of the following: kieselguhr, kaolin, sand, pumice.gypsum, chalk, or any other cheap chemically inert material.

The following are examples of compositions which are found to besatisfactory:

Example No. 1

Parts Pumice 6.0 Kaolin 4.0 Potassium chlorate 1.5 Aluminum 3.0 Brass2.0 Cuprous oxide 1.0 Linseed oil 0.1

p-Toluene sulfonic acid 0.6

Example No. 2

Parts Pumice 6.0 Kaolin 4.0 Potassium chlorate 1.5 Aluminum 4.0 Cuprousoxide 1.0 Mineral oil 0.1 Benzene sulfonic acid 0.6

diluent may vary from 5 to 20 parts, the aluminum from 1 to 6 parts,-thebrass from 0.05 to 5 parts, the potassium chlorate from 0.4 to 5 parts,the cuprous oxide from 0.05 to 4 parts. The proportion of the sulfonicacid or mixture of sulfonic acids which may be used may vary widelywithout departure of the composition from functioning for a specificpurpose, depending upon the polarity, water-solubility and neutralequivalent of the acid or mixture of acids selected. The oil may beeliminated entirely or used in quantities as stated or substantiallylarger according to the mass of the other ingredients involved.

It is obvious that numerous combinations of ingredients mentioned couldbe selected from the above disclosure and the quantities varied to givedifferent results as to extent and degree of heating. All suchcompositions are considered as em bodying the present invention whenthey are characterized by the presence of a metal and by the productionof hydrogen or hydrogen ions from a sulfur-containing acid or acids, andby means of the addition of water or a moistening medium to an otherwiseinert mass, to combine with an oxidizing agent in an exothermicoxidation-reduction reaction or reactions. The exclusive use of theseand other modifications of the invention as described in theaccompanying claims is contemplated.

What is claimed is: I v

1. A composition for producing heat by chemical action, comprising amixture of a metallic component selected from the group consisting ofmagnesium, aluminum, manganese, iron, cadmium, zinc, copper, tin,bismuth, antimony, lead, and active alloys of the same, a water solubleorganic acid containing sulfur as a part of the acid group and stable inthe dry state and capable when in solution of furnishing an acidicmedium, and an oxidizing agent sufllciently active in said acidic mediumto oxidize said metallic component.

-2. A composition for producing heat by chemical action, comprising amixture of a metallic component'selected from the group consisting ofmagnesium, aluminum, manganese, iron, cadmium, zinc, copper, tin,bismuth, antimony, lead, and active alloys of the same, a water solubleorganic sulfonic acid stable in the dry state and capable when insolution of furnishing an acidic medium, and an oxidizing agentsuillciently active in saidacidic medium to oxidize said metalliccomponent.

3. A compositiorrfor producing heat by chemical action, comprising amixture of a metallic component selected from the group consisting ofmagnesium, aluminum, manganese, iron, cadmium, zinc, copper, tin,bismuth, antimony, lead, and active alloys of the same, an organic acidsulfate stable in the dry state and capable when in solution offurnishing an acidic medium, and an oxidizing agent sufllciently activein said acidic medium to oxidize said metallic component.

4. A composition for producing heat by chemical action, comprising amixture of a metallic component selected from the group consisting ofmagnesium, aluminum, manganese, iron, cadmium, zinc, copper, tin,bismuth, antimony, lead, and active alloys of the same, an organic acidcontaining sulfur in the dry state and capable when in solution offurnishing an acidic medium, and an oxidizing agent sufilciently activein said acidic medium to oxidize said metallic component, the organicacid furnlshingthe acidic medium being selected from the, groupconsisting of sulionic acids whichare represented by the formula RSOzH,where R is a substituted or unsubstituted. aliphatic or aromaticradical.

5. A composition for producing heat by chemimium, zinc, copper, tin,bismuth, antimony, lead,

and active alloys of .the same, an organic acid containing sulfur in thdry state and capable when in solution of furnishing an acidic medium,and an oxidizing agent sumciently active in said acidic medium tooxidize said metallic component, the organic acid furnishing the acidicmedium being selected from the group consisting of acid sulfates whichare represented by the formula R'OSOaI-I, where R is a substituted orunsubstituted, aliphatic or aromatic radical.

6. A composition as described in claim 1 in which the oxidizing agent isselected from the group consisting of barium peroxide, benzoyl peroxide,potassium dichromate, potassium permanganate, the persulfate of ammoniumand the alkali metals, the perborates oi the alkali metals, thechlorites, chlorates and perchlorates of magnesium and. the alkalimetals.

'7. A composition as described in claim 1 which also includes anaccelerating ingredient insoluble in water and stable in the mixture butbeing rendered active in the acidic medium.

8. A composition as described in claim 1 which also includes anaccelerating. ingredient selected from the group consisting of'cuprousoxide and c'upric oxide.

9. An exothermic mixture including aluminum,

potassium chlorate, cuprous oxide, and an organic sulfonic acid.

10. An exothermic mixture including aluminum, potassium chlorate,cuprous oxide, and an organic acid sulfate.

11. An exothermic mixture including aluminum, brass, potassium chlorate,cuprous oxide, and an organic sulfonic acid.

12. An exothermic mixture including aluminum, brass, potassium chlorate,cuprous oxide, and an organic acid sulfate.

13. An exothermic mixture comprising aluminum, approximately 4 parts byweight; potassium chlorate, approximately 1.5 parts; cuprous oxide,

approximately 1.0 part by weight; a water soluble organic sulfonic acid,approximately 0.6 part by

